We started by looking at arithmetic and geometric sequences and sums.
Arithmetic is more like addition, geometric has more to do with multiplication.
Subscripts are used as labels. If the number is next to a letter, it looks like multiplication.
Separating a number with a summation for an exponent into two pieces can be useful.
And either ln or log is often useful for problems with exponents (especially when they are more complicated).
One test problem was worded in a strange way.